The present invention relates to balloon catheters such as are used for dilation and/or fluid-delivery purposes, and particularly to such catheters for dilating a stenosis or occlusion in a body duct while maintaining fluid flow through the duct. The invention is especially useful for treating a stenosis or occlusion in a blood flow passage, and is therefore described below with respect to such an application, but it will be appreciated that the invention could also be used in many other applications.
Balloon catheters are used at the present time for opening stenoses or occlusions in coronary arteries or in other parts of the vascular system. A widely used treatment is called percutaneous transluminal coronary angioplasty (PTCA), which makes use of a dilatation catheter having a distensible portion in the form of an inflatable balloon at the distal end of the catheter. The physician, using fluoroscopy, guides the catheter through the vascular system until the distensible portion is positioned across the stenosis. The balloon is then inflated by supplying fluid under pressure through an inflation lumen leading to the balloon, to open the artery and to reestablish acceptable blood flow.
A primary concern of PTCA is the temporary blockage of blood flow during balloon inflation. Various perfusion dilation catheters have been developed to provide a path for blood flow through the distensible portion of the catheter during the inflation of the balloon. Examples of such known catheters are described in U.S. Pat. Nos. 4,581,017, 4,790,315, 4,944,745, 4,592,340 and 5,344,402. One of the as yet unsolved problems in such catheters is simultaneously providing three critical features: (1) high blood flow rate with a low flow resistance when the balloon is inflated; (2) a small catheter profile when the balloon is deflated to facilitate its insertion into the blood vessel; and (3) simplicity of operation. Ideally, a low-profile perfusion catheter would achieve high blood perfusion rates without requiring the operator to perform any function in addition to the balloon inflation.